Ignition systems, which generate a high voltage with the aid of which combustible mixtures of a spark ignition internal combustion engine are ignited, are known in the related art. For improved controllability of the ignition spark energy, to reduce electrode wear and to achieve additional advantages, the related art provides for combining an ignition coil with a step-up converter, the step-up converter supplying electrical power to an ignition spark generated with the aid of the ignition coil. The step-up converter converts an input voltage into a higher output voltage. During the ON phase of the switch of the step-up converter, the inductor (storage choke) of the step-up converter is charged with power. With the switch open, this power is transferred to the output capacitor across the diode of the step-up converter. If the switch (for example, an IGBT or a MOSFET) is triggered by pulse width modulation, for example, then the output voltage is a function of the pulse duty factor, among other things. Such a storage choke is often designed as a toroidal core having a ferrite core gapped by an air gap in the related art. An output voltage of approximately 6 kV is typically required for use of a step-up converter in an ignition system. Electronic switches (for example, IGBT or MOSFET) generally cannot be used for such high voltages. Their maximum switching voltages are in the range of 600 V to 1000 V. However, due to the design of the storage choke as a transformer having a transformation ratio of 1:10 or 1/10, for example, the voltage at the switch may be reduced from approximately 6 kV to 600 V. Such a transformer could also be designed as a toroidal core, for example. However, the disadvantages here are obvious to those skilled in the art:                Toroidal core windings are difficult to automate.        The wire ends are mostly tin-plated and must be selectively soldered to the circuit board.        The output voltage of 6 kV, for example, must be insulated with respect to the ferrite core, which may be comparatively complex and may be achieved, for example, by extrusion coating.        The secondary winding must be electrically insulated with respect to the primary winding. Wires for these voltages are virtually unavailable on the market. The outside diameters of the available wires are too large for use in a toroidal core transformer, the volume of which is to be kept preferably small. Foil insulations between the primary winding and the secondary winding are also impossible, given the intended overall size.        
One possible design for the transformer to be used according to the present invention includes a multipart shell-core design (for example, in two parts, three parts or four parts) including a ferrite core gapped by an air gap. The primary winding and the secondary winding here are wound onto a coil bobbin, the wire ends are placed in contact pockets and contacted by cold contact (for example, by an insulation displacement connection (ID connection)). The contact with the circuit board may include a solder connection or cold contact, such as a Flex Pin, for example.
However, the disadvantages mentioned above, in particular with regard to the required insulation, are not solved with the shell-core transformers known in the related art.